Saturday, August 7, 2021

'Graphene' - The Future of Engineering (Part 2)

Part - 2

1) Monolayer sheets

In 2013, different scientist came together and they presented a production unit. This unit helps to produce graphene monolayer sheets. This production unit uses liquid metal matrix on which graphene gets grow. This process creates polycrystalline graphene know as high strength metallurgical graphene (HSMG). Grolltex is one of the famous manufacturing industries of the monolayer sheets. They can produce monolayers up to 8 inches diameter.

2) Bilayer graphene

As the name bilayer itself indicates that it consists two layers of graphene. This form of graphene is used in optoelectronic and nanoelectronics applications. Bilayers shows tuneable band gap and excitonic condensation makes form very special in above mention applications. There are different types of stacking of the two layers. AA-stacked bilayer, AB-stacked by layer and twisted bilayer are the methods to stack. First bilayer was formed in the year 2004 by Mr. Geim. CVD is the effective technique to produce bilayers in the large scale.

3) Graphene superlattices

Superlattices formed by stacking graphene layers which provide fascinating structural element and highly functional atomic scale. This form of graphene is widly used in nanoelectronics and photonic devices. Phonon (quantum of vibration of mechanical) thermal transport can be visualized with help of superlattices. This is the ideal model which makes possible to understand the wave like and particle like study of phono.

4) Nanoribbons

Graphene nanoribbons are also known as nano graphite ribbons having width of just 100nm. Mitsutaka Fujita first introduced the nanoribbons to the world. It is very difficult to produce nanoribbons precisely. It has the value of Youngs modulus of over 1 TPa. Its edge structure is the zigzag manner which decides the electronic states of ribbon.

5) Quantum dots

Graphene quantum dots (GQds) are nano particles of the graphene. They are less than 100nm in the size having properties like low toxicity, chemical stability as well as quantum confinement effect. They are used in biological, energy and environment applications.

1) 6) Graphene oxide

Graphene oxide formed by using paper making techniques which oxidized the graphite element forms the single sheets with strong bonds. It has tensile strength of 32 GPa. It enhanced the photo conducting properties of the polymers. As graphene is the vacuum-tight material but after converting into the graphene oxide water and vapour easily gets passed through it.

7) Graphene fibre

Scalable and controllable CVD method is effective way to produce graphene films precisely and this form rose in 2011. CVD delivered tuneable morphology as well as the pore structure by controlling evaporation of solvents with precise surface tension. Graphene fibres first used in supercapacitors in 2013 in the solid state. Fibres provide thermal and electrical conductivity in the greater way, with the highest mechanical strength. It is widely used in the textile industry, light weight vehicles, micro electronic devices. It has 80GPa tensile strength.

1) 8) 3D graphene

Graphene atoms are hexagonally arranged in such way that they form the three-dimensional honeycomb structure formed 3D graphene. CVD is mostly used methods to produce 3D structure. 3D graphene came into the picture in the year 2013 by stony Brook. He fabricated 3D porous and free-standingarchitecture of graphene. He used radical initiated crosslinking method. Mr. Khurram introduced new technique of the production that is then-state-of-the-art for the 3D graphene structure in the year 2016. These 3D graphene are used in the energy storage, filtration, thermal management and biomedical devises.

9) Pillared graphene

Pillared graphene is one of the hybrid carbon structure. It consists oriented array of nanocarbon connected at end of the graphene sheets. This concept arose in 2008 in the mind of George Froudakis and he described theoretically in the university of Crete in Greece. It is not implemented yet but it has the great future in the electronic industry. Its poses useful electronic properties. It can be also useful for hydrogen storage tank material.

10) Aerogel

One of the interested forms of graphene is Aerogel. It weighs just 0.16 milligrams per cm³. Aerogel is obtained from the solution of graphene and carbon nanotubes. This solution first freezes dried and then dehydrate the solution which produced the Graphene aerogel. This form has the superior elasticity. It can recover 90% of the compression. Its absorption capacity is also great which can absorb up to 900 times of its own weight. The rate of absorption is 6808 grams per seconds. It is the lightest material form ever.

1) 11) Nano coil

Nano coils are discovered in the year of 2015. Production of nano coils is possible because of the defect in the material having the hexagonal grids which cause it to spiral along its edge. When we apply voltage to this nano coils, flowing current around this coil produced the magnetic field. Solenoid made up of these coils acts as the quantum conductor. Its current distribution varies in between of core and the exterior walls which produced nonlinear inductance.

12) Crumpled graphene

Crumped graphene has wrinkles on the material in the nanoscale. This technique of crumpling on the graphene is introduced by the Brown university in the year of 2016. For getting this form of graphene the shrink films are used on which graphene oxide layer deposit. The graphene oxide gets converted into the superhydrophobic crumpled graphene which is used in the battery electrodes.

Application of Graphene:

A. Applications in Energy industry

1) Solar cell

From many of the year’s scientist work to develop lighter, flexible and transparent solar cells. But the Major problem was of finding of such material which has all the properties and able to carry current. Indium Tin oxide has been used because it poses all the properties except flexibility. But discovery of graphene changes the traditional way and in 2017 researchers managed to apply graphene on solar cells. So, the flexible and transparent solar cells were produced which can be mount on cars, cloths, cell phones, etc.

1) Batteries

Graphene enhanced the working of traditional lithium batteries. It provides longer lifespan, higher capacity as well faster charging time. Graphene batteries are light in weight and flexible which makes them to use in the wearable electronics.

A. Applications in medicine

1) Graphene in Dialysis

As graphene plays various roles in all industry. With addition to that is also able to filter the blood. Researchers showed that it can be used to filter blood from chemical and drugs as well. Superiority of graphene is 20 times greater than the traditional methods.

1) 2) Photothermal therapy

Photothermal therapy is used to eliminate abnormal cells by irradiating special agent which destroy those cells with the help of heat. Graphene oxide increase the working and the effectiveness of this therapy. With the help of graphene oxide, we can implement both chemo therapy and photothermal therapy combinedly. So that it will give better result of destroying tumours. Doing this therapy, it can not damage the healthy cells.

A. Applications in electronics

1) Transistors

Graphene replaces the silicon in the production of transistors. This increases speed of computers up to 1000 times. This will lead technology on the next level as it saves the time and increases the functionality. Graphene will make the world faster. Graphene provides high carrier mobility and creates very low noise.

2) Waterproof and Wearable electronics

Major problem of electronic devices is that they get damaged when they come in contact of the water. Graphene is the best solution on such problems. Graphene is strong, transparent and able to conduct electricity. That’s why engineers of Lowa state university print the circuits of the device with the help of graphene flake. With waterproof electronics scientist are also working on wearable electronics. Graphene made flexible batteries printed on a fabric. This will create electronic environment friendly and smart e-textile which can store energy. This will send all digital gadgets in to the history.

1) 3) Flexible and touchscreen

Indium tin oxide (IOT) is used commercially for the screen of smartphones, computer, etc. Researchers of Rice university developed graphene thin films for smartphone which beats the IOT. Graphene provides lower resistance and the higher transparency which increase the performance of digital devices. Chine has produced flexible smart phones with help of graphene. This graphene screens are are strong light in weight and transparent. It gives all the requirement of smartphone working with great satisfaction. Smart phones made up of graphene weighs 200 grams only. Hence graphene will bring the technology on the next level in the future.

A. Applications in sports

1) 1) Shoes

Graphene is not purely used in shoes but it is used in composite form. It is proven that sole made of graphene have a life of hundreds of years. University of Manchester and sport Invo-8 brand produced shoes made up of graphene. These shoes increase the strength and provide flexibility properties increased by 50%. These shoes are more durable than traditional. Graphene shoes are able to absorb shock and the impact which could damage the bones and joints. It protects the body part most efficiently.

1) 2) Rackets

Graphene is upgrades energy distribution equally. Weight of racket gets reduced whereas the service speed and the stability gets increased. Tennis equipment company named as HEAD developed the graphene racket series whose name is “GRAPHENE 360 SPEED PRO”. Novak Djokovic used this racket for the first times. Graphene will give better performance in the sport field also.

Home Assignment Activity By -

SYDA _B_ Batch - 2_Group - 2

51 - Ahire Mrunal Keshav

52 - Mathpati Vaishnavi Vikas

53 - Sonawane Pushkar Mukesh

54 - Jagtap Sanket Rajendra

55 - Chavan Sanskruti Suresh

Guided By :

Prof. N. S. Kulkarni

Prof. S. V. Patil

'Graphene' - The Future of Engineering

Bansilal Ramnath Agarwal Charitable Trust's

Vishwakarma Institute of Technology

(An Autonomous Institute affiliated to Savitribai Phule Pune University)

Vishwakarma Institute of Technology, 666, Upper Indiranagar, Bibwewadi , Pune, Maharashtra, INDIA - 411 037.

Contact No. +91 - 20 - 2428 3001

GRAPHENE

Graphene is one of the carbon allotropes and one atom thick layer of carbon connected by hybridized bonds. Its layers are arranged in two-dimensionalhexagonal structure which is called as honeycomb lattice. The name is derived from the element graphite having -ene as the suffix in which -C=C- has been attributed highest priority in the organic compound. Each and every atom of graphene is connected to its three nearest atoms by strongest types of sigma bond. Graphene is also known as the mother of different graphitic forms present up to date. It has remarkable property is that energy of electrons is dependent linearly on the wave vector near the crossing points in the Brillouin zone.

Graphene: - mother of all graphitic forms

Discovery of Graphene: -

P. R. Wallace Was the first who explored graphene very first time in 1947 as starting point for understanding properties of 3D graphite. Hanns-Peter Boehm published a study in 1961-62 of extremely thin flakes of graphite and introduced the term “GRAPHENE”. In 1984 Gordon Walter Semenoff and David DiVincenzo emphasized the occurrence of magnetic field of an electronic level precisely at Dirac point which describes unusual electron transport properties of material. Transmission electron microscopy (TEM) works on the single sheets of graphite. It was used in the description of carbon nanotubes by R. Saito and Mildred in 1992 as well as in 2000 for polycyclic aromatic hydrocarbons by S. Wang.

Finally, Richard L. Dudmanas well as Robert B. Rutherford filed for a patent in 2002 to produce graphene by repeatedly peeling off layers from graphite flake adhered to subtract, achieved graphite thickness of 254 Nanometer. Graphene was isolated in proper manner and characterized at university of Manchester by Andre Geim and Konstantin Novoselov in 22 October 2004. By using adhesive tape, they pulled graphene layers form graphite in process calledMicro-mechanical cleavage or exfoliationtechniques. It is used to obtained single layer or atomically thin sheets of the graphene. It is also carried out by electrostatically as well as by using electromagnetism in air, vacuum or inert environment. In 2014 National Graphene Institute was established for further studies.

Production of Graphene: -

Now a days graphene used in many commercial applications. According to the need there are various production techniques of the graphene.

Mechanical way of production: -

1. Mechanical exfoliation

Mr. Geim and Mr. Novoselov used adhesive tape for extraction of the grapgene from the graphite. But for getting single layer of graphene, multiple exfoliation steps are required. By doing this we get thin layer called as flakes which is deposited on silicon wafer. But these flakes of graphene are visible to naked eyes. As technology gets developed the number of defects in flakes gets reduced and mobility of electrons is highest as of 2014. The sharp single crystal diamond wedge are used to divide layers of graphite. As well as in the year 2014, an unoxidized graphene with liquids were made by scientist which was defect free.It is made up of graphite with the help of mixers that produce local shear rate greater than 10 * 10⁴.

2. Ultrasonic exfoliation

By using Sonification with centrifugation method spreading graphite in a liquid medium, graphene can be obtained. Heptane and water are used as ionic liquid for dispersing. Surfactant is used as solvent before the sonication to prevent restacking helps to increase the concentration at higher level. Sonication of graphite in between two liquids, heptane and water produced macro scale graphene films.

Splitting monolayer carbon

Nanotube slicing and fullerene splitting

One of the easiest is to opening carbon nanotubes by cutting it, and putting it in potassium permanganate and sulfuric acid to get graphene. In Fullerene splitting method, spraying buckyballs at supersonic speed on to the substrate, the balls get open by cracking and result into the unzipped cages. Then form a bond in between them to form films of graphene.

Chemical Way of production: -

1. Molten salts

In this method graphite particles are allowed to corrode in the molten salts which forms different nanostructures, one of them is graphene. We can observe that Hydrogen cations can be discharged on graphite which is cathodically polarized as hydrogen is dissolved in molten lithium chloride and from that cathode, we can peel odd the graphene sheets. These nanosheets are of high degree of crystallinity with the great thermal stability.

2. Electrochemical synthesis

We can also exfoliate graphene by electrochemical synthesis. The graphite is first immersed in the solvent for intercalation purpose and by varying voltage we get required properties as well as in controlled manner.

3. Hydrothermal self-assembly

This method is easy and safethan other techniques. It is also environmental free than the exfoliation techniques. From sugar like glucose, fructose graphene has been prepared. This method is also known as Tang-Lau method as we can extract multilayers.

4. Microwave assisted oxidation

By using microwave energy, we can produce graphene in just one step and this process occurred in 2012. Because of this method the use of potassium permanganate is excluded. Just what have to do is to control the microwave time to synthesized the graphene with micro wave radiation assistant.

Chemical vapor deposition

1. Epitaxy

In this process, silicon slices coated with germanium are keep in to the dilute hydrofluoric acid which create hydrogen terminated germanium with the coat of graphene on it by CVD.

2. Cold wall

With help of cold wall CVD, the rate of production of graphene gets increased by 100 times than the conventional CVD method as well as cost gets reduced by 99%. The produced material has the enhanced electronic qualities.

Carbon dioxide reduction

In this process the magnesium combusts because of the exothermic reaction. Because of that in oxidation or reduction reaction, the nanoparticles of carbon get produced. On that carbon nanoparticles we get the graphene.

PROPERTIES OF GRAPHENE

1. Physical properties

Graphene is the thinnest material with 0.34 nm thickness and toughest 2D material ever. It is much harder than the steel and the diamond having same dimensions. It has the tensile strength 130 GPa with stiffness more than 1 TPa. 0.3 inches of graphite contains 3 million graphene layers. It is incredible stretchy and flexible, so that it can gets stretch up to 25% of its original length. Graphene is two-dimensional material even then it is visible without any microscope. One more interesting property is that it gets expand when it gets cooled and shrinks when it gets warm. There is not a single material of the same quality. Its density is 0.763 mg per m² .

2. Electronic properties

As graphene is a zero-gap material it has extremely high electrical current density, because conduction and the valence bands meet at the Dirac points. The resistance offered by graphene is less than other material. Also, it is able to convert into the superconductor which carry 100% electricity. There no bandgap, hence it is used for transistor production. Its intrinsic mobility is 100 times better than silicon thus electrons have no resistance when they move through graphene.

3. Thermal conductivity

Graphene is the best thermal conductor which has the highest thermal conductivity as compared to other materials. It is greater than carbon nanotubes and diamond. As well as graphene is able to conduct heat in all direction and that’s why it is isotropic conductor.

4. Optical properties

One remarkable property is that graphene absorbs extreme amount of light near about 2.3% of white light and because of that a single layer also we can see with naked eyes. By this property I can be used as solar cells and transparent conductors. The optical response of graphene nanoribbons is tuneable into the terahertz regime by an applied magnetic field.

5. Chemical properties

Graphene is inert material as it does not react with other substances even its all atoms are exposed to environment. It absorbs different atoms and molecules still doesn’t react with them. This property makes is special and can lead in the future. Also, it’s the material whose both sides all atoms available for reaction purpose. That’s why it has special chemical reactivity and the highest ratio of edge atoms of any allotrope. Its boiling point is 4200^oC.

Forms and Application of Graphene (See in Part 2)

https://vitech21.blogspot.com/2021/08/graphene-future-of-engineering-part-2.html